As the cost of energy continues to escalate and the world continues to push to reduce its environmental impact, the need and desire to operate industrial machinery more efficiently increases. The drying of washed linens in a laundry dryer is an energy intensive process. Wet linens are loading into the dryer and spun in a rotating tumbler. A blower takes air from either the room around the dryer or from a duct connected to outside air and sends it past a heating source. The heating source heats the incoming air and it then directs the air into the rotating tumbler. Within the tumbler the hot air encounters the wet linen and in the process the water on the linens evaporates into the air. The air then flow out of the dryer and is exhausted away from the inlet air. The process continues until the linens are free of undesirable moisture.
In a perfect operation, the heated air would be at an extremely low humidity level. It would then remain in the tumbler until the humidity was 100% and cool to approximately the temperature of the source air and thus the air is completely saturated before being exhausted out of the dryer. However, this type of operation is not possible due to operational constraints and the need for productivity in a wash environment. Thus, dryers exhaust air is generally severely elevated in temperature compared to the ambient air, a temperature that increases as the linens within the dryer become more dry. It is this lost heat in the dryer exhaust air, that accounts for the energy inefficiency of the typical drying process.
Heat recovery wheels have long been used in commercial ventilation applications to allow for adequate ventilation of buildings without loss or gain of undesirable heat energy in the ventilation process. These wheels are known as “enthalpy wheels.” However, in this type of application, both the incoming and exhaust air are relatively clean of foreign particles. The same cannot be said for the laundry drying process. The exhaust air which enters the apparatus is both moist and laden with lint particles from the linens being dried. The moist particles have a tendency to stick to the heat recovery wheel which caused the wheels to clog and dramatically reduce operating efficiency.
It would be desirable to have a cleaning apparatus to keep the heat recovery wheel both clean and efficient thus providing for a more effective way to transfer the heat from the dryer exhaust into the dryer inlet air. By preheating the inlet air, the amount of heat required by the dryer heating source, whether it be a steam coil, oil coil, electric element or fuel burner, to get the dryer air temperature up to and maintained at the desired level could reduced.